Trait indexmap::map::MutableKeys

source ·
pub trait MutableKeys {
    type Key;
    type Value;

    // Required methods
    fn get_full_mut2<Q>(
        &mut self,
        key: &Q
    ) -> Option<(usize, &mut Self::Key, &mut Self::Value)>
       where Q: Hash + Equivalent<Self::Key> + ?Sized;
    fn retain2<F>(&mut self, keep: F)
       where F: FnMut(&mut Self::Key, &mut Self::Value) -> bool;
    fn __private_marker(&self) -> PrivateMarker;
Expand description

Opt-in mutable access to keys.

These methods expose &mut K, mutable references to the key as it is stored in the map. You are allowed to modify the keys in the hashmap if the modification does not change the key’s hash and equality.

If keys are modified erroneously, you can no longer look them up. This is sound (memory safe) but a logical error hazard (just like implementing PartialEq, Eq, or Hash incorrectly would be).

use this trait to enable its methods for IndexMap.

Required Associated Types§

Required Methods§


fn get_full_mut2<Q>( &mut self, key: &Q ) -> Option<(usize, &mut Self::Key, &mut Self::Value)>where Q: Hash + Equivalent<Self::Key> + ?Sized,

Return item index, mutable reference to key and value


fn retain2<F>(&mut self, keep: F)where F: FnMut(&mut Self::Key, &mut Self::Value) -> bool,

Scan through each key-value pair in the map and keep those where the closure keep returns true.

The elements are visited in order, and remaining elements keep their order.

Computes in O(n) time (average).


fn __private_marker(&self) -> PrivateMarker

This method is not useful in itself – it is there to “seal” the trait for external implementation, so that we can add methods without causing breaking changes.



impl<K, V, S> MutableKeys for IndexMap<K, V, S>where K: Eq + Hash, S: BuildHasher,

Opt-in mutable access to keys.

See MutableKeys for more information.


type Key = K


type Value = V